1. Would it be ok to hook up the heat exchanger after the return from a propane heater. My thoughts were to open up next year with the 400k/btu propane heater and heat exchanger simultaneously and once up to temp shut off the propain$$$$, just have the heat exchanger running.

2. What do you guys use to regulate the temp going to the heat exchanger zone? aquastat? not necessary? I typically run my pump 4 hours a night would I need to run more frequently? or is this going to be enough to maintain temp with the 200k btu heat exchanger. I would like the water between 80F, much hotter is not desirable. Sometimes I get a 10-15 degree drop overnight plan on getting a solar cover next year to counter act a bit.

18,000Gal pool w/ 1.8 HP pump using the BBB method from troublefreepool.com works great for me. S260 Boiler, 200ft run to pool

This has to be one of the best explainations on Boiler sizing I have read in a while,,

EarthWindandFire wrote:I am posting this for future reference:

The goal is to have a heater that has enough capacity to heat the pool to your desired level in a reasonable amount of time. Maintaining that temperature is a lot easier once the pool is up to temp.

First, the capacity of most pool heaters are rated in BTU's or British Thermal Units. One BTU is the amount of heat required to raise the temperature of one pound of water, one degree F. And since there are 8.33 gallons of water per pound, it takes 8.33 BTU's to raise one gallon of water, one degree F.

Now let's calculate:

1. Determine the number of gallons in your pool (G).

2. Determine the amount in temperature that you want to raise the pool temp (the easiest way to figure this is to use the air temp as the minimum and the desired pool temp as the maximum) (Delta T).

3. Calculate the number of BTU's needed (BTU) per gallon of water by multiplying step 2 x 8.33. Multiply this number times the gallons of water in your pool (G). This is the number of BTU's to raise your pool temp from the minimum to desired temp.

4. Determine how FAST you want to be able to go from the minimum temp to the desired temp (in hours) (H).

5. Divide the total number of BTU's from step 3 by the hours in step 4 to yield the BTU'S per hour that your heater will need to deliver.

6. Multiply Step 5 by a error factor of 20% and add to step 5. This is approximately the size of heater that you will need.